Pain threshold rises with altered brain chemistry

The number of opiate receptors in the brain, critical in the modulation of pain behaviour, increase to combat severe pain in arthritis sufferers, according to a study.

It has been known for a long time that we have receptors in our brains that respond to natural pain killing opiates such as endorphins, but the researchers at the University of Manchester have now shown that these receptors increase in number to help cope with long-term, severe pain.

The study also explains as to why some people seem to cope better than others with pain.

By applying heat to the skin using a laser stimulator, Christopher Brown and his team showed that more the opiate receptors there are in the brain, the higher the ability to withstand the pain.

The study used Positron Emission Tomography (PET) imaging on 17 patients with arthritis and nine healthy controls to show the spread of the opioid receptors.

"This is the first time these changes have been associated with increased resilience to pain and shown to be adaptive," Brown said.

"Although the mechanisms of these adaptive changes are unknown, if we understand how we can enhance them, we may find ways of naturally increasing resilience to pain without the side effects associated with many pain killing drugs," he added.

Professor Anthony Jones, director of the Manchester Pain Consortium which focuses on improving the understanding and treatment of chronic pain, said, "This is very exciting because it changes the way we think about chronic pain."

"It may be that some simple interventions can further enhance this natural process, and designing smart molecules or simple non-drug interventions to do a similar thing is potentially attractive."

"Anything that can reduce reliance on strong medication must be worth pursuing," said Val Derbyshire, a patient with arthritis.

The paper, 'Striatal opioid receptor availability is related to acute and chronic pain perception in arthritis: Does opioid adaptation increase resilience to chronic pain?', was published in the journal Pain.